The present invention relates to the use of syntactic foams for printing. More particularly, this invention relates to syntactic foam compositions suitable for printing two and three-dimensional graphic designs and the like on various substrates including, but not limited to, paper and textile fabrics and to methods of using this foamed composition.
The formation of a permanent, good quality graphic representation or decorative pattern on a highly adsorbent and/or very irregular substrate surface such as coarse paper or textile fabrics has traditionally involved a multiple of problems due to the rough and uneven surface characteristics of such substrates. Numerous printing formulations have been developed over the years in an attempt to render such surfaces more receptive to print and recently, aerated foams have generated much interest. However, such foams are not readily suitable for use with modern, high speed printing equipment due to variations in foam density which render the foam highly unstable.
Accordingly, one of the primary goals of the textile printing industry is to develop improved, stable foams exhibiting excellent print quality, hand and fastness properties equivalent to conventional pigment print systems. In addition, such foams must be capable of withstanding the ever increasing line speeds characteristic of high speed printing operations and must have the proper rheological characteristics to withstand application on roller print as well as flat and rotary screen print machines at high speeds.
To accomplish this goal, precise formulations exhibiting certain specified properties must be developed. Among those factors to be considered are blow ratios, viscosity, bubble size and foam stability. Blow ratio is defined as the relationship obtained by dividing the weight of a given volume of an unfoamed system by the weight of the same volume of the resultant foamed system. The higher the blow ratio, the more air is present in the foamed composition. A decreasing blow ratio can produce off shading and color darkening. Even minor variations in blow ratio or density produce undesirable color variations in the print.
If the foam cell size increases beyond a certain point, a motley print may result. Preferred cell size is between 50 and 100 microns. Cells or bubbles, in this range produce creamy foams with good printing characteristics. Uniformity of bubble size is also important for foam stability. Foams containing air bubbles of nonuniform size require constant monitoring by a computer or other means in order to assure the maintenance of a constant viscosity.
Moreover, paper and textile printing and finishing operations are highly energy intensive with most of the energy consumed used to evaporate excess water present in the print medium. Since the most efficient energy conserving system would use air in foam form to replace water, extensive efforts are underway within the printing industry to produce better foamed formulations having greater stability which will further conserve energy and reduce production costs.